Surface mounting package

ABSTRACT

A surface mounting package includes a metal base with a lower surface having a through hole, a metal lead arranged to be inserted into the through hole, an insulating material filling in an internal space defined by the metal base, a cap covering the metal base as a lid, and an electronic part component arranged at a surface on the internal space side of the metal lead. The internal space is held at an air-tight atmosphere. The metal base has a lower surface positioned on the same plane as a lower surface of the metal lead or the insulating material, the same plane forming a plane to be attached to a mounting board.

TECHNICAL FIELD

The present invention relates to a surface mounting package for anelectronic part component, and in particular, to a structure in which ametal lead is adhered to a metal base by an insulating material andexposed to the outside.

BACKGROUND ART

In a device such as a quartz resonator, a filter or an oscillator, as anelectronic part for surface mounting, a surface mounting package to be ahousing contains an electronic part component such as a piece of quartz,a piezoelectric device or the like. Examples of such a surface mountingpackage typically include four types of structures each having a baseand a cap, as will be described below with Conventional Examples 1 to 4.

CONVENTIONAL EXAMPLE 1

A surface mounting package of Conventional Example 1 is formed, as shownin FIGS. 10 and 12, by first connecting a metal lead 6 for lead-out to acircular metal base 5 by a high-melting glass 7 which is an insulatingadhesive (e.g. borosilicate), and then combining a cylindrical cap 8shown in FIG. 11 therewith such that an opening end 8 e is coupledaround metal base 5 for sealing. As can be seen from FIG. 13,cylindrical cap 8 has legs 9 for holding its position, connected bywelding or the like to an outer periphery of the cylindrical portion.Cylindrical cap 8 in such a package is made of metal for preventingentry of external electromagnetic wave that interferes with the functionof a quartz resonator and the like.

CONVENTIONAL EXAMPLE 2

A surface mounting package of Conventional Example 2 is shown in FIG.14. The package is formed by combining a box-shaped ceramic base 9 witha platy ceramic cap 10 for covering a box opening 9 a. Only an insulatoris used as a material for the package. If there is no concern aboutentry of electromagnetic wave, the package may be made of an insulatoralone as in Conventional Example 2, not using a metal material as inConventional Example 1.

CONVENTIONAL EXAMPLE 3

A surface mounting package of Conventional Example 3 is shown in FIG.15. The package is formed by combining ceramic base 9 and a translucentglass cap 11 that serves as a top plate to cover a ceramic base opening9 a, and sealing the package with low-melting glass 31. The package usesa glass cap, so that oscillation frequency after sealing can easily beadjusted by laser trimming.

CONVENTIONAL EXAMPLE 4

A surface mounting package of Conventional Example 4 is shown in FIG.16. The package is formed by combining ceramic base 9 with a metal cap12. A metal thin film 14 (e.g. silver brazing filler metal) is formed onan upper surface at the opening side of a spacer 13 forming sidewalls ofceramic base 9. Metal thin film 14 and metal cap 12 are connectedtogether by seam welding or electron-beam welding.

The surface mounting package according to Conventional Example 1,however, needs to ensure insulation between metal lead 6 and metal base5 by providing an insulating material around metal lead 6, whichincreases the outer diameter of the package by a distance required forinsulation, and thus adversely affects thinning of the package. As forother conventional techniques, each of the surface mounting packagesaccording to Conventional Examples 2 to 4 has a limit on thinning of thepackage, since it is difficult to reduce a bottom-plate thickness 15 ofthe base due to constraints in the composition and characteristics ofceramic base 9 used as a base material. Excessive reduction in thedimension would adversely affect the air tightness, moisture resistanceand strength of the package.

DISCLOSURE OF THE INVENTION

In view of the conventional circumstances as described above, an objectof the present invention is to provide a surface mounting package thatallows further reduction in the thickness.

To achieve the object, a surface mounting package according to thepresent invention employs a metal base in place of the combination of aninsulating ceramic base and a cap. A metal lead for lead-out is providedat the bottom of the metal base having a surface to be attached to amounting board. The metal lead is configured to have a lower surfacecoplanar with a lower surface of the metal base. By using metal as abase material, the bottom portion of the base, which had to be madethick to a certain degree when a ceramic base was used, can be madethinner. Moreover, the strength of the package can also be secured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a thin metal package as a surface mountingpackage in the first embodiment of the present invention;

FIG. 2 is a section view taken along line II—II in FIG. 1 in thedirection of the arrow;

FIG. 3 is a section view taken along line III—III in FIG. 1 in thedirection of the arrow;

FIG. 4 is a plan view of a thin metal package as a surface mountingpackage in the second embodiment of the present invention;

FIG. 5 is a section view taken along line V—V in FIG. 4 in the directionof the arrow;

FIG. 6 is a section view taken along line VI—VI in FIG. 4 in thedirection of the arrow;

FIG. 7 is a plan view of a thin metal package as a surface mountingpackage in the third embodiment of the present invention;

FIG. 8 is a section view taken along line VIII—VIII in FIG. 7 in thedirection of the arrow;

FIG. 9 is a section view taken along line IX—IX in FIG. 7 in thedirection of the arrow;

FIG. 10 is a section view showing the metal package in ConventionalExample 1 of the surface mounting package;

FIG. 11 is a section view taken along the direction of axis of acylindrical cap for the metal package in Conventional Example 1 of thesurface mounting package;

FIG. 12 is a section view taken along line XII—XII in FIG. 10 in thedirection of the arrow;

FIG. 13 is a section view taken along line XII—XIII in FIG. 11 in thedirection of the arrow;

FIG. 14 is a section view of the ceramic package in Conventional Example2 of the surface mounting package;

FIG. 15 is a section view of the ceramic package in Conventional Example3 of the surface mounting package; and

FIG. 16 is a section view showing the package in Conventional Example 4formed by combining a metal cap with a ceramic base.

BEST MODES FOR CARRYING OUT THE INVENTION

The present invention will clearly be understood by the followingdescription of embodiments.

First Embodiment

The first embodiment of a surface mounting package for a quartzresonator according to the present invention will be described withreference to FIG. 1. In the present embodiment, the surface mountingpackage includes an assembled base 4 in which a metal base 1 and a metallead 2 are adhered together by an insulating material 3, and a metal cap30 illustrated by a chain double-dashed line. Metal base 1 constitutingassembled base 4 forms a metal cavity structure (i.e. a structure inwhich a part of a metal box is cut out) as shown in FIG. 1, and has abase bottom portion 16 provided with a through hole 160. Metal lead 2 isof a quadrangular prism with an inner surface 2 i and an outer surface 2o of the six surfaces serving as an inner electrode and an outerelectrode, respectively. Metal lead 2 is shaped to be accommodated tometal base 1 and is inserted into a position corresponding to throughhole 160. It is noted that FIGS. 2 and 3 are section views taken alonglines II—II and III—III, respectively, in FIG. 1 in the direction of thearrows.

A surface 2 o which is to be the lower surface of metal lead 2 and thelower surface of base bottom portion 16 form a plane P used when thepackage is attached to a mounting board. Plane P may be flat when it isfixed by brazing to a flat printed board or the like, but is formed tobe a curved plane when it is attached to a cylindrical surface, toconform thereto.

Further, a gap space generated when metal lead 2 is inserted into metalbase 1 is filled with e.g. borosilicate glass, which is high-meltingglass, as an insulating material 3. Heat is applied to weld theinsulating material, to adhere metal lead 2 to metal base 1. It isunderstood that Ag-based glass which is low-melting glass may be used asinsulating material 3 for an electronic part component susceptible tohigh-temperature adhesion.

A quartz piece is fixed to a pair of lead electrodes 2 on assembled base4 configured as described above. Metal base 1 is covered and coupledwith a metal cap 30 indicated by chain double-dashed lines in FIGS. 2and 3. In order to allow adjustment of oscillation frequency by applyingultraviolet light to an electronic part component after a surfacemounting package is completed, borosilicate glass may be used in placeof metal cap 30, in consideration of translucency.

Second Embodiment

The second embodiment of a surface mounting package for a quartzresonator according to the present invention will be described withreference to FIG. 4. The surface mounting package includes assembledbase 4 in which metal base 1 and metal lead 2 are adhered together byinsulating material 3, and a metal cap (not shown). Metal base 1constituting assembled base 4 forms a metal cavity structure (i.e. astructure in which a part of a metal box is cut out) as shown in FIG. 1,and has base bottom portion 16 provided with two through holes 161, 162as shown in FIG. 5. Metal lead 2 is of a quadrangular prism, twosurfaces 2 i and 2 o of the six surfaces serving as an inner electrodeand an outer electrode. Metal lead 2 is shaped to be accommodated tometal base 1 and inserted into a position corresponding to each ofthrough holes 161, 162. It is noted that FIGS. 5 and 6 are section viewstaken along lines V—V and VI—VI, respectively, in FIG. 4 in thedirection of the arrows.

Further, a gap space generated when metal lead 2 is inserted into metalbase 1 is filled with insulating material 3 of high-melting glass. Heatis applied to weld the insulating material, to adhere metal lead 2 tometal base 1. Here, insulating material 3 may not necessarily be made ofa glass-based material. For instance, polyimide-based resin and the likemay also be used when the glass-based material is unacceptable due tothe specification of an electronic part component.

As an electronic part component, for example, a piezoelectric device isfixed to a pair of lead electrodes 2 on assembled base 4 configured asdescribed above. Metal base 1 is covered and coupled with metal cap 30(not shown). It is noted that an oscillator including a filter and asemiconductor device may also be employed as an electronic partcomponent. Metal lead 2 is not limited to a bar-shaped one with arectangular section, but may have an approximately circular shape whenthe electronic part component uses small power and employs low currentrating. Moreover, if a surface mounting package completely-shielded fromelectromagnetic wave is desired, metal cap 30 may be formed, forexample, of an Fe—Co—Ni alloy.

Third Embodiment

The third embodiment of a surface mounting package for a quartzresonator according to the present invention will be described withreference to FIG. 7. The surface mounting package includes assembledbase 4 in which metal base 1 and metal lead 2 are adhered together byinsulating material 3, and a metal cap (not shown). Metal base 1constituting assembled base 4 forms a metal cavity structure (i.e. astructure in which a part of a metal box is cut out) as shown in FIG. 1,and has a base bottom portion 16 provided with one through hole 160.Metal lead 2 is of a quadrangular-prism-like shape having a curvedsurface, two surfaces 2 i and 2 o of the six surfaces serving as aninner electrode and an outer electrode. Metal lead 2 is shaped to beaccommodated to metal base 1 and inserted into a position correspondingto through hole 160. It is noted that FIGS. 8 and 9 are section viewstaken along lines VIII—VIII and IX—IX in FIG. 7, respectively, in thedirection of the arrows.

Further, a gap space generated when metal lead 2 is inserted into metalbase 1 is filled with borosilicate glass, which is high-melting glass,as insulating material 3. Heat is applied to weld the insulatingmaterial, to adhere metal lead 2 to metal base 1.

A piezoelectric device is fixed to a pair of lead electrodes 2 onassembled base 4 configured as described above. Metal base 1 is coveredand coupled with a metal cap (not shown). Here, for example, Ag-basedglass may also be used as insulating material 3 when an electronic partcomponent desires no high-melting glass as an insulating material.

While the lower surface of metal lead 2 was coplanar with that of metalbase 1 in the embodiments above, the lower surface of insulatingmaterial 3, instead of metal lead 2, may have the same plane as thelower surface of metal base 1. Alternatively, as illustrated, the lowersurfaces of metal lead 2, insulating material 3 and metal base 1 may allbe on the same plane.

As can be understood from the description above, the surface mountingpackage according to the present invention eliminates the need forproviding an insulating material around a metal lead as in aconventional package (Conventional Example 1), allowing the package tobe made thinner and smaller. By changing a base material from ceramic tometal, the air tightness, moisture resistance and strength of thepackage can be secured even if the base bottom plate portion has a smallthickness.

INDUSTRIAL APPLICABILITY

The present invention may be applicable to a surface mounting packageused in surface mounting of an electronic part component such as aquartz resonator, a filter, an oscillator and the like, and is useful infurther thinning of the surface mounting package.

1. A surface mounting package, comprising: a metal base with a lowersurface having a through hole; a metal lead arranged in said throughhole; an insulating material filling in an internal space defined bysaid metal base; a cap covering said metal base as a lid; and anelectronic part component arranged at a surface on said internal spaceside of said metal lead, said internal space being held at an air-tightatmosphere, said metal base having a lower surface positioned on a sameplane as a lower surface of said metal lead, said same plane forming aplane to be attached to a mounting board.
 2. The surface mountingpackage according to claim 1, wherein said plane to be attached is aflat plane.
 3. The surface mounting package according to claim 1,wherein said plane to be attached is a curved plane.
 4. The surfacemounting package according to claim 1, wherein said electronic partcomponent is adhered by a high-melting solder.
 5. The surface mountingpackage according to claim 1, wherein said metal lead is a bar with arectangular section.
 6. The surface mounting package according to claim1, wherein said metal lead is a bar with an approximately circularsection.
 7. The surface mounting package according to claim 1, whereinsaid insulating material is high-melting glass.
 8. The surface mountingpackage according to claim 1, wherein said insulating material islow-melting glass.
 9. The surface mounting package according to claim 1,wherein said insulating material is a polyimide-based resin material.10. The surface mounting package according to claim 1, wherein said capis made of a metal Fe—Ni—Co alloy.
 11. The surface mounting packageaccording to claim 1, wherein said cap is borosilicate glass.
 12. Thesurf ace mounting package according to claim 1, wherein said insulatingmaterial has a lower surface positioned on said same plane.
 13. Asurface mounting package comprising: a metal base including a bottomplate portion having a first lower surface, and having a through holethat penetrates from said first lower surface through a thickness ofsaid bottom plate portion and that is bounded by said metal base allaround a perimeter of said through hole; a cap covering said metal baseso as to enclose and seal an interior cavity between said cap and saidmetal base; a metal lead arranged in and extending through said throughhole, from a second lower surface of said metal lead lying on a samecommon plane with said first lower surface of said bottom plate portion,into said interior cavity; an insulating material filling a remainder ofsaid through hole all around said metal lead between said metal lead andsaid perimeter of said through hole; and an electronic componentarranged in said interior cavity and connected to said metal lead;wherein said common plane of said first lower surface and said secondlower surface forms a mounting plane of said surface mounting packageadapted to be attached to a mounting board.
 14. The surface mountingpackage according to claim 13, wherein said insulating material has athird lower surface lying on said same common plane with said first andsecond lower surfaces.
 15. The surface mounting package according toclaim 13, wherein said metal base further includes a sidewall portionprotruding from said bottom plate portion away from said first lowersurface toward said cap, said through hole further extends to andpenetrates through a thickness of said sidewall portion, and said metallead further extends laterally outwardly through said thickness of saidsidewall portion in said through hole.
 16. The surface mounting packageaccording to claim 13, wherein a longest dimension of said metal leadextends laterally, parallel to said bottom plate portion, along saidsecond lower surface that lies on said same common plane with said firstlower surface.